Strip accumulators heretofore have stored a length of strip material in an expanding and contracting spiral coil having a fixed number of turns with the strip material being fed to the inside of the spiral coil and withdrawn from the outside, or vice versa. Typically, the maximum diameter of the outermost turn of the spiral coil is determined by an outer containment ring or circular array of outer containment rollers whereas the inner diameter of the innermost turn of the spiral coil is determined by an inner containment ring or circular array of inner containment rollers. Accordingly, the difference between the length of coil when fully expanded into engagement with the outer containment ring or rollers and when fully contracted against the inner containment ring or rollers determines the maximum reserve storage capacity of the accumulator for any given gauge and number of turns of the strip material.
In one known type of strip accumulator disclosed in U.S. Pat. No. 3,860,188, an annular ring or array of long, thin, cylindrical rollers support a single spiral coil of strip material with the axis thereof oriented vertically, and such rollers are synchronously driven by individual variable-speed electric motors to rotate the spiral coil of strip material supported thereon to facilitate feeding and withdrawal of the strip material from the spiral coil. The rollers extend radially, or may be slightly skewed and slope downwardly and outwardly to urge the turns of the spiral coil stored thereon outwardly as the rollers rotate.
For feeding the strip material to the innermost turn of the spiral coil, a helical feed-in mechanism is provided which typically includes a driven pair of feed-in or pinch rollers mounted on a helix support cage consisting of one or more pairs of fixedly mounted guide idler rollers which define a desired helical path for the strip material from the pinch rollers to the individually driven rollers supporting the spiral coil.
Although such known feed-in mechanism has been found to operate satisfactorily with heavy gauge strip material, problems have occurred when feeding lighter gauge or very flexible strip material. The lighter gauge strip material may bend or bow as it is fed into and through the helix support cage. When this occurs, it is necessary to remove the bend or bow in the strip material or otherwise the strip material will not properly feed into the accumulator. Sometimes the bend or bow can be removed by manually pushing thereon, but usually it is necessary for the strip material to be backed out of the helix and flattened which is both difficult and time consuming. Moreover, the entire processing line would have to be stopped while the strip material is backed out of the support cage and straightened which obviously has an adverse effect on overall productivity of the processing line.